INTEGRATED BUCK?FLYBACK NON ISOLATED PFC CONVERTER WITH CONSTANT ON-TIME CONTROL

An integrated buck?flyback non isolated power factor correction converter is proposed in this paper. This new converter is an inherent integration of a buck converter and a flyback converter, which operates in either flyback mode or buck mode according to whether the input voltage is lower or higher than the output voltage. In this way, the dead zones of ac input current in traditional buck power factor correction converter can be eliminated. Therefore, the proposed integrated buck?flyback power factor correction converter can achieve high power factor under universal ac input range, and its input current harmonics can be reduced. Conventional Buck power factor correction converter and proposed converter are simulated using MATLAB/Simulink. A 10W laboratory prototype of the proposed power factor correction converter with 12V input voltage was setup using PIC 16F877 microcontroller. Compared to conventional power factor correction converters, the power factor was improved greatly with the proposed topology especially at low line. This proposed topology is very suitable for high-power non isolated LED drivers with high power factor requirements